As Sugardaddy1979 mentioned, you can buy parts for your current single stage regulator. When you decide to purchase a dual stage regulator, you can easily swap the parts to the new regulator without any problems.

You can check my Primer to Pressurized CO2 (linked in my signature below) as well as Bettatail's Needle/metering valve list for part numbers, if you are interested in assembling your own setup.